tracing service: improve logging for --save-for-bugreport
tracing service: improve logging for --save-for-bugreport

Adding some extra logging to debug --save-for-bugreport emitting
zero length files occasionally.

Bug: 188008375
(cherry picked from commit 167d67c2e7d38922c1c616f77a12510c4835c7f4)
Change-Id: I1f8b0385b3c3956bd8b8209ebb36ce3878ec42be
Merged-In: I1f8b0385b3c3956bd8b8209ebb36ce3878ec42be

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto